Pressure relief valve with damping piston



Feb. 2, 1954 PRESSURE RELIEF VALVE WITH DAMPING PISTON J. M. TOWLER ETAL Original Filed Feb. 17, 1944 2 Sheets-Sheet l M Attorney 9 J. M.TOWLER ET AL 2,667,894

PRESSURE RELIEF VALVE WITH DAMPING PISTON Original Filed Feb. 17, 1944 2Sheets-Sheet 2 Iriuentor S WWM M Attorney Patented Feb. 2, i9542,667,894 PRESSURE RELIEF VALVE WITH DAMPING PISTON John Maurice Towler,Harrogate, and Frank Hathorn Towler, Otley, Electraulic Presses Limited,

England, assignors to Rodley, England,

a corporation of England Original application February 17,

Divided and this application February 20, 1948, Serial N0. 9,854

Claims priority, application Great Britain March 9, 1943 Claims.

This invention relates to hydraulic reducing or relief valves of thetype in which the liquid, the flow of which is to be controlled, actingupon one end of a valve plunger moves said plunger against an opposingspring, weight, or other load and in which the return movement of theplunger is damped by means comprising a damping piston.

The object of the present invention is to simplify the construction ofthe reducing or relief valve according to our co-pending applicationSerial No. 522,842, filed February 1'7, 1!?44 (now abandoned), and ofwhich this application is a division, and the improvement ormodification consists in forming the passage which conveys the pressureliquid from the inlet or outlet to the outer side of the piston withinthe piston itself and not in the valve body as before and in providing avalve of the needle type on the underside of the valve plunger forclosingsa d passage to prevent the free escape of the liquid and so dampthe return movement of the valve plunger.

In order that the invention may be clearly understood and carried intoeffect two embodiments of the same will now be described by way ofexample, by aid of the accompanying drawings in which:

Fig. l is a vertical section through a relief valve, shown in the partlyopen position, having a single cut-oil and constituting one of theaforesaid embodiments according to this invention,

and

Fig. 2 is a similar view showing the application of the improvementsaccording to the present invention to a reducing or relief valve havinga double cut-off. This valve is shown in the fully open position.

Referring now to Fig. 1 of the drawings, the valve therein illustratedcomprises a body composed of three superimposed sections, an uppersection I, an intermediate section 2 and a lower section 3. The upperbody section I is bored to receive a bush 4 and this bush in turn isbored and lapped to receive, as a close sliding fit, a packinglessplunger 5, constituting the valve member proper. This plunger 5 isreduced at 5a for a predetermined distance from its lower end and at theextremity of said reduced portion it is turned to a point to form aneedle valve 6 for a purpose hereinafter described.

Ihe bush A is smaller in diameter than the recess in the upper section Iin which it is located, to provide an annular space 8. This space 8 isin open communication with exhaust and it also communicates with thebore containing the 1944, Serial No.

plunger 5 by means of two or more transverse passages 9. When theplunger is in its lower or closed position it closes the inner ends ofthese passages 9.

The intermediate section 2 of the valve body is bored axially toaccommodate a piston It and transversely to provide a straight-throughpassage l l for pressure liquid passing from the inlet H! to the outletl3. This transverse passage is bisected by the vertical bore containingthe piston l0, and said piston is formed with a reduced portion I4 toprovide a clearance around which the liquid may flow in its passage fromthe inlet I2 to the outlet l3. The piston It has a central hole I5extending through its interior from the bottom of the piston to within ashort distance of the opposite end. The passage thus formed is continuedthrough the upper portion of the piston by means of a substantiallysmaller hole 16. There is thus provided a passage from one end of thepiston to the other through which pressure liquid from the passage 1 imay be per mitted to pass into a space H beneath the lower end of thepiston. Normally this passage through the piston is closed at the outerend of the hole It by the needle valve 6. The piston I0 is held againstthis needle valve when the valve member or plunger 5 is in the closedposition by a small spring It in the space H, and the plunger 5 isloaded against lift by a spring I9.' The load thus applied by the spring[9 may be adjusted by a screw adjustment. Consequently, the valve may beset to blow ofi at a iven pressure.

In operation, and assuming a sudden rise in pressure within the passagel l, the plunger 5 will be forced upwards against the spring 19 and awayfrom the piston it thus causing the hole it in the piston l0 to beopened and allowing the .pressure balance to be restored on theunderside of the piston. Immediately the pressure balance is restoredthe small spring 58 will move the piston l0 upwards until the needlevalve again closes the hole is. Liquid within the space H is thustrapped and can only escape slowly past the piston. In consequence thedownward movement both of the plunger 5 and the piston Ill imparted bythe spring it will be at a relatively slow speed. In other words suchmovement will be damped. The fall in pressure of, the liquid acting uponthe underside of the plunger 5 will occur in consequence of theresulting upward movement of the plunger as such movement will bring itsreduced portion 5a into correspondence with the passages 9, as shown inFig. 1, thus con- In Fig. 2 the improvements according to the presentinvention are shown applied to a reducing valve having a double cut-01finstead of the, single'cut-off shown in Fig. 1. Corresponding parts areidentified by the same reference numerals as in Fig. 1, but beingprimed. In this modification the inlet I 2' and the outlet 13 are notconnected by a straight-through passage as in Fig. l but are connecteddinally spaced passages which are opened and closed by movement of thevalve plunger.

The above mentioned passages comprise two sets of radial passages 20 and2|, one set 20 connecting the bore containing the plunger with a lowerannular chamber 22 receiving pressure liquid from the inlet I2, and theother set 2! connecting said bore with an upper annular chamber 23 whichin turn is connected to the outlet It by a passage 24.

Cut in the exterior surface of the valve plunger 5' so as to encirclethe same are grooves 25.

by two sets of longitu- 7 slidable in the These grooves are spacedlongitudinally a distance equivalent to the distance between the centresor" the sets of radial passages 20 and 2|, with which they register whenthe valve plunger is in the raised position shown in the drawing. Thegrooves 25 communicate with a longitudinal passage 26 within theinterior of the valve plunger by means of radial holes 21. By this meansa passage for liquid is provided between the annular chambers 22 and 23when the valve plunger is in the raised position, and said chambers areisolated from each other when the valve plunger is in the loweredposition. In this embodiment pressure liquid from'the inlet [2' has freeaccess to an annular space 28 surrounding the damping piston H! by meansof a passage 29 in the valve body. The function of the piston It! inthis embodiment is the same as in the first embodiment.

The damping means of the present invention may be appli d to the mastercontrol valve illustrated in Fig. 2 of our 'co-pending applicationSerial No. 522,844, filed February 17, 1944, now Patent No, 2,561,431issued July 24 1951. 'For the purpose of the adaptation the lower end ofthe valve plunger in the said master control valve is provided with theneedle valve 6 as in Fig. 2 of the present application whilst for thedamping piston 2| of the co-pending application there is thensubstituted the piston l0 and the intermediate and lower sections of thevalve body illustrated in present Fig. 2.

We claim:

1. A hydraulic valve comprising a body having a valve bore and apressure liquid inlet and an outlet spaced from said inlet axially ofsaid bore, passages connecting said inlet and said outlet wit said bore,a plunger slidable in the bore for closing and opening a communicationbetween said passages, means for maintaining said plunger in a normalcommuniction closing position with a predetermined force, a dampingpiston slidable in the valve body having means normally maintaining saidpiston in disengageable end contact with the plunger, the inner end ofsaid piston being exposed to the pressure in said bore, a chamber in thevalve body at the outer end of said piston, a passage for admittingpressure liquid from said inlet to said chamber, valve means connectedto said plunger for opening said passage during the movement of saidplunger to its communication opening position aforementioned dueto apredetermined rise in the pressure of the liquid, and for closing saidpassage during the return movement of the plunger to its normal positionto prevent free ;escape of the liquid from said chamber, and

means independent of leasing the liquid from said valve means for resaidchamber at a comparatively slow rate, whereby to damp the returnmovement of the plunger.

2. A hydraulic valve comprising a body having a pressure liquid inletand an outlet spaced from said inlet, a bore, passages connecting saidinlet and said outlet with said bore, a plunger bore for closing andopening communication between said passages, means for maintaining saidplunger in a normal communication closing position with a predeterminedforce, a cylinder in the valve body, a damping piston separable fromsaid plunger and slidable in said cylinder and having means normallymaintaining said piston in end contact with the plunger, said pistonhaving a diameter substantially greater than the diameter of the plungerand being exposed at the inner end to the .pressure in said bore, apassage having a flow restriction therein and for admitting pressureliquid from said inlet to the outer end of said cylinder, valve meansoperable with said plungerrfor normally closing said last mentionedpassage and for opening said passage during the movement of said plungerwhile separated from said piston to its communication opening positionaforementioned due to a predetermined rise in the pressure of theliquid, and for closing said passage during the return movementof theplunger while in contact with said piston to its normal position toprevent free escape of the liquid from said cylinder, clearance spacebetween said cylinder and said piston slowly permitting release of theliquid from said cylinder by leakage past said piston.

3. A reducing valve comprising a body having a pressure liquid inlet andan outlet longitudinally spaced from said inlet,

close said communications with a predetermined force, a damping pistonslidable in the valve body coaxial with the plunger and having means atthe outer end of said piston, tending longitudinally through the pistonfor admitting pressure liquid to said chamber, a valve at the end of theplunger opposed to the piston functioning to open said passage during Ithe movement of the plunger to open the aforementioned communicationsbetween the inlet and the outlet upon a predetermined rise in thepressure of the liquid and to close said passage during the returnmovement of the plunger to its normal position to prevent free escape ofthe liquid from said chamber, and means providing slow escape of liquidfrom said chamber whereby to damp said return movement of the plunger.

4. A relief valve comprising a valve body having an inlet for pressureliquid and an outlet, a passage for the free fiow of the pressure liquidfrom said inlet to said outlet, an exhaust outlet, a plunger slidable insaid body having a reduced portion extending from one end thereof andexposed at said reduced end to the pressure of the liquid in saidpassage, means maintaining said plunger in a normal position to isolatesaid passage from said exhaust outlet with a predetermined force andmovable upon predetermined increase in the pressure of the liquid to aposition wherein said reduced portion thereof establishes communicationbetween the aforementioned passage and the exhaust outlet, whereby thepressure in the passage is caused to fall to normal and the plunger isreturned to its normal position aforesaid, a piston slidable in thevalve body coaxial with the plunger and having means normallymaintaining said piston in end contact with said plunger, a chamber atthe outer end of said piston, a passage extending longitudinally throughthe piston, a needle valve at the end of the plunger opposed to thepiston, functioning to open said piston passage to admit pressure liquidto said chamber during the movement of the plunger to establishcommunication between the aforementioned passage and the exhaust outlet,said needle valve closing said piston passage during the return movementof the plunger to its normal position to prevent free escape of theliquid from said chamber, and means providing slow escape of liquid fromsaid chamber whereby to damp said return movement of the plunger.

5. A hydraulic valve comprising, in combinatien, a body having apressure liquid inlet, a flow passage in communication with said inlet,an outlet, a passage in communication with said outlet, a valve bore,ports respectively connecting said passages to said bore, and a cylinderchamber in axial alignment with said bore, the adjacent ends of saidbore and chamber being in intercommunication and in communication withsaid flow passage, a valve plunger reciprocable in said bore and beingmovable to open or close communication between said ports, spring meansnormally urging said plunger into closed position, a damping pistonreciprocable with peripheral leakage clearance in said chamber, a valvepassage opening axially through said piston and having a valve port atthe inner end, a pointed valve rigid on one end of said plunger andengageable with said valve port to close the latter, and spring means insaid chamber and acting on said piston to urge said piston inwardlynormally to effect engagement of said valve and valve port.

JOHN MAURICE TOWLER. FRANK I-IATHORN TOWLER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 982,400 Walker Jan. 24, 1911 1,291,609 Nichols Jan. 14:, 19191,850,117 McMillan Mar. 22, 1932 1,970,131 Douglas Aug. 14, 19342,200,824 Herman May 14, 1940 2,286,027 Towler June 9, 1942

